Fraction defective estimating method, system for carrying out the same recording medium

ABSTRACT

A method and a system for estimating an assembling-related fraction defective coefficient of an article in the stage preceding to manufacturing, e.g. at a stage of design. Assembling operation, properties/conditions of parts to be assembled and conditions of an assembling shop having significant influence to the likelihood of occurrence of failure in assembling work are inputted as data. Estimated value of assembling-related fraction defective is arithmetically determined with high accuracy by executing an assembling-related fraction defective value estimating program on the basis of the data as inputted.

This is a continuation of application Ser. No. 09/566,482, filed May 8,2000 now U.S. Pat. No. 6,553,273; which is a continuation of Ser. No.09/048,988, filed Mar. 27, 1998, now U.S. Pat. No. 6,108,586.

BACKGROUND OF THE INVENTION

The present invention relates to a method and a system for evaluatingqualities of articles such as electric/electronic apparatuses for homeuse, products for office-automation (OA) and the like which aremanufactured by assembling constituent parts. More particularly, thepresent invention is concerned with a fraction defective estimatingmethod for estimating likelihood of occurrence of failure in the worksinvolved in assembling an article, a system for carrying out thefraction defective estimating method and a storage medium storingtherein data, information and program for executing the method.

Methods known heretofore for determining the fraction defective areprimarily so designed as to estimate the causes for occurrence ofdefects, failures or the like, starting from the defect events orfailure phenomena which have actually taken place. As the hitherto knowntypical methods of estimating the cause of failure or detect on thebasis of the contents of the failure phenomenon or the defect eventactually or really taken place at a stage in the course of manufacturingprocess, there may mentioned those disclosed in Japanese UnexaminedPatent Application Publication No. 167631/1989 and Japanese UnexaminedPatent Application Publication No. 196900/1994. These methods are basedon such techniques that real records of defects occurred in the past arestored together with data concerning the causes of such defects in orderto allow a degree of correlation between a defect pattern and the causefor the defect to be determined, whereon the cause for the defect isestimated on the basis of the correlation as determined. Further, as thediagnosis techniques in which the similar techniques are adopted, theremay be mentioned those disclosed in Japanese Unexamined PatentApplication Publication No. 13617/1995 and Japanese Unexamined PatentApplication Publication No. 271587/1995.

However, any one of the known methods mentioned above is directed to thetechnique for estimating directly the causes of defect events or failurephenomena on the basis of the contents of such defects or failures whichhave really taken place for the purpose of allowing correcting orrepairing work to be carried out speedily and properly.

On the other hand, as a method or procedure for performing in advance aquality evaluation of an article to be manufactured before failure ordefect really occurs, there is known an FMEA (Failure Mode and EffectsAnalysis) technique which can already be adopted in the stage ofdesigning the article to be manufactured. According to this method, anevaluator himself or herself predicts “failure phenomena which may occurin relation to individual parts constituting an article” and summarizesthe “failure phenomena or events together with relations to theindividual parts in the form of a list. Thus, by referencing the list,the evaluator himself or herself can predict “what sort of influence thearticle as manufactured will suffer when certain failure(s) or defect(s)occurs”. In this way, high-quality design suffering substantially nounintentional omissions can be realized.

Further, there is known a method or procedure for estimating seriousnessof defects or failures relating to individual parts, respectively, bydetermining the probability of occurrence of failure phenomenon inrelation to the individual parts as estimated by the evaluator (whichprobability is termed the fraction defective) and then estimating thedegree of seriousness of defect of an article as manufactured which canbe considered as being ascribable to the defect(s) of the individualparts. As a typical one of such techniques, there may be mentioned FMECA(Failure Mode, Effects and Criticality Analysis) technique.

However, any one of the conventional methods or techniques mentionedabove is not in the position to estimate the potential of detectorfailure to occur in a given article with high accuracy. This is becausesubstantially all the failure phenomena which may actually occur have tobe grasped in the case of the conventional methods.

Under the circumstances, not a few manufacturing failures actually takeplace due to insufficiency of examination or studying, presenting one ofthe factors for deterioration of the quality of the manufacturedarticle.

SUMMARY OF THE INVENTION

In the light of the art described above, it is an object of the presentinvention to provide a method and a system for estimating the potentialof occurrence of failure in assembling a given article already in thestage preceding to manufacturing process, e.g. at a stage of design,manufacturing process planning or the like.

At this juncture, it should be mentioned that with the term “part” usedherein, it is contemplated to encompass both an elementary part and anassembled part or subassembly constituted by a plurality of theelementary parts. Accordingly, with a phrase “part attaching work”, itis intended to encompass both the attaching works not only for anelementary part but also an assembled part, respectively. Further, anelementary part or an assembled part which is to be attached to anotherelementary part or assembled part will be collectively referred to as“attachment-destined part” while the latter which is subjected to orundergoes the attachment will be referred to as “attachment-subjectedpart”.

In view of the above and other objects which will become apparent as thedescription proceeds, it is taught according to the present inventionthat an estimated value of assembling-related fraction defective whichindicates likelihood of occurrence of defectives in an assembled articleis determined on the basis of information concerning factors which exertinfluence to the probability of occurrence of failure in relation to theoperations which are involved in part attaching works and which can notalways be performed by a worker without fail. (The probability mentionedabove will hereinafter be referred to also as the uncertainty.)

In a preferred mode for carrying out the invention, the estimated valueof the assembling-related fraction defective is arithmeticallydetermined on the basis of information concerning the contents ofoperations involved in part attaching works, information concerningproperties of an attachment-destined part or parts and informationconcerning properties of an attachment-subjected part or parts.

To this end, according to an aspect of the present invention, species ortypes of operations required for expressing the contents of theoperations involved in the part attaching works (such as operation fordownward movement, operation for horizontal movement and the like whichare correctively referred to as standard attaching operation) aredetermined, and numerical values indicating low or high probabilitiesthat standard attaching operations can not be performed without failunder predetermined conditions inclusive of “condition imposed by anoperator or worker, condition imposed by a part and conditions imposedby a work-shop” (these conditions will be referred to as basicconditions) is determined or set for each of the standard attachingoperations as determined. (The numerical values mentioned above will bereferred to also as the standard-attachment-operation-based fractiondefective coefficient.)

In another mode for carrying out the invention, an object underevaluation is expressed in terms of a combination of preset standardattaching operation elements for the purpose of facilitating userinterface.

Furthermore, according to another aspect of the present invention, it istaught with a view to enhancing the estimation accuracy of theassembling-related fraction defective that in addition to theaforementioned standard attaching operation elements used for expressingthe contents of attaching operations involved in the part attachingwork, properties of the attachment-destined part and theattachment-subjected part which exert influence to the uncertainty ofthe attaching operation are expressed in terms of part-condition-relatedsupplementary factors mentioned below, whereon the estimated value ofthe assembling-related fraction defective is arithmetically determinedon the basis of the part-condition-related supplementary factors. Morespecifically, the factors exerting influence to the uncertainty ofattaching work performed by a worker among the properties of theattachment-destined part and the attachment-subjected part (thesefactors are referred to as the part-condition-related supplementaryfactors) are determined, whereon for the part attaching work for anobject for which the assembling-related fraction defective is to beestimated, those part-condition-related supplementary factors which arerelevant to the properties of the attachment-destined part orattachment-subjected part in the part attaching work of concern areselected from the preset part-condition-related supplementary factorsmentioned above for expressing the contents of the attaching operationin addition to the expression given in terms of combination of thestandard attaching operations as mentioned above.

According to another aspect of present invention, it is taught with aview to enhancing further the accuracy in estimating theassembling-related fraction defective that for the part attaching workin assembling an article for which the fraction defective is to beestimated, information indicating whether a step or process forconfirming if the part attaching work of concern has been performedcorrectly and properly is provided or not in succession to theassembling work process is used in addition to the standard attachingoperation elements expressing the contents of attaching operationinvolved in the part attaching work and the part-condition-relatedsupplementary factors giving influence to the uncertainty of theattaching operation, for thereby arithmetically determining theestimated value of the assembling-related fraction defective.

According to a further aspect of the present invention, it is taughtwith a view to enhancing further the accuracy in estimating theassembling-related fraction defective that the estimated value of theassembling-related fraction defective is arithmetically determined onthe basis of a numerical value (referred to as the shop constant)indicating degree of influence of the shop conditions and reflecting thefactors exerting influence to the uncertainty of the attaching operationsuch as the condition imposed by the worker, the condition imposed byequipment installed in the assembling shop, environmental condition andthe like for the part attaching work in addition to the standardattaching operation elements expressing the contents of attachingoperation involved in the part attaching work, thepart-condition-related supplementary factors exerting influence to theuncertainty of the attaching operation and the information indicatingwhether a step or process for confirming if the part attaching work ofconcern has been performed correctly and properly is provided or not insuccession to the assembling work process.

According to a still further aspect of the present invention, it istaught that the fraction defective coefficients each for each of theindividual standard attaching operations of the attachment-destinedpart, the supplementary coefficients each for each of the properties ofthe attachment-destined parts and the supplementary coefficients eachfor each of the properties of the attachment-subjected parts are storedin advance, wherein the information representing the combination ofpredetermined standard attaching operations for expressing an objectunder evaluation and the information representing the properties of anattachment-destined part and the attachment-subjected part of the objectunder evaluation are inputted, whereon the fraction defectivecoefficients for the standard attaching operations of concern, therelevant supplementary coefficient for the attachment-destined part andthe relevant supplementary coefficient for the attachment-subjected partare extracted from the inputted information, to thereby arithmeticallydetermine the assembling-related fraction defective of the object underevaluation by adding together the values resulting from supplementationof the individual fraction defective coefficients as extracted with thesupplementary coefficients for the attachment-destined parts and thosefor the attachment-subjected parts.

According to a yet further aspect of the present invention, there isprovided a fraction defective estimating system which includes a meansfor storing fraction defective coefficients each for each of individualstandard attaching operations for attachment-destined parts,supplementary coefficients each for each of properties of theattachment-destined parts and supplementary coefficients each for eachof properties of attachment-subjected part, a means for inputtinginformation representing a combination of predetermined standardattaching operations for expressing an object under evaluation as wellas information representing the properties of the attachment-destinedparts and the attachment-subjected part of an object under evaluation,and a means for extracting the fraction defective coefficient for thestandard attaching operation of concern, the relevant supplementarycoefficient for the attachment-destined part and the relevantsupplementary coefficient for the attachment-subjected part from theinputted information, to thereby arithmetically determine anassembling-related fraction defective for the object under evaluation byadding together values resulting from supplementation of the individualfraction defective coefficients as extracted with the supplementarycoefficients for the attachment-destined parts and those for theattachment-subjected parts.

Furthermore, according to the present invention, there is provided sucharrangement that when fraction defective coefficients for every standardattaching operation for attachment-destined parts, supplementarycoefficients for every property of an attachment-destined part,supplementary coefficients for every property of attachment-subjectedparts, information representing a combination of predetermined standardattaching operations for expressing an object under evaluation and theinformation concerning properties of the attachment-destined parts andthe attachment-subjected part constituting the object under evaluationare inputted, fraction defective coefficients for relevant standardattaching operations, supplementary coefficients relating to theattachment-destined part and supplementary coefficient relating to theattachment-subjected part are extracted from the input information, forthereby arithmetically determining an assembling-related fractiondefective of the object under evaluation by adding together valuesobtained by supplementing the extracted individual fraction defectivecoefficients with the supplementary coefficients relating to theattachment-destined part and those relating to the attachment-subjectedparts. The procedure described above can be executed by a computationunit with the aid of a program designed properly to this end.

In this conjunction, it is preferred to store previously thesupplementary coefficients for every number of attachments to be carriedout for thereby arithmetically determining an assembling-relatedfraction defective by supplementing the aforementioned fractiondefective coefficient with the supplementary coefficient relating to thenumber of attachments required in realizing the object under evaluation,or store previously a supplementary coefficient corresponding topresence or absence of a process for confirming whether theattachment-destined part has been properly attached to theattachment-subjected part, for thereby arithmetically determining anattachment-related fraction defective of the object under evaluation bysupplementing additionally the fraction defective coefficient with thecorresponding supplementary coefficients in the case where there existsthe process for confirming whether the attachment-destined part has beenproperly attached to the attachment-subjected part.

The above and other objects, features and attendant advantages of thepresent invention will more easily be understood by reading thefollowing description of the preferred embodiments thereof taken, onlyby way of example, in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the course of the description which follows, reference is made to thedrawings, in which:

FIG. 1 is a schematic block diagram showing generally and schematicallya system configuration of a fraction defective estimating system forestimating a fraction defective in an assembling work according to anembodiment of the invention;

FIG. 2 is a functional block diagram illustrating functions performedinternally by the fraction defective estimating system;

FIG. 3A is a view showing typical examples of standard attachingoperations and symbols indicating the operations, respectively, in adatabase;

FIG. 3B is a view showing some examples of part-condition-relatedsupplementary factors together with corresponding symbols;

FIG. 4 is a view illustrating, by way of example, data in a database ofstandard-attaching-operation-based fraction defective coefficients inthe system according to an embodiment of the invention;

FIG. 5 is a view showing, by way of example, data ofoperation-sequence-related supplementary coefficients;

FIG. 6 is a view illustrating, by way of example, data in a database ofsupplementary coefficients relating to part conditions of anattachment-subjected part;

FIG. 7 is a view showing, by way of example, contents of a shop constantdatabase;

FIG. 8 is a view showing, by way of example, data in a database ofcheck-process-related supplementary coefficients;

FIG. 9 is a flow chart for illustrating a procedure for arithmeticallydetermining an estimated value of an assembling-related fractiondefective in a part attaching work;

FIG. 10 shows views for graphically illustrating examples ofsupplementary coefficient pattern which can be employed in carrying outthe invention;

FIG. 11 is a view showing a computation model for computing estimatedvalue of the assembling-related fraction defective according to theinvention;

FIG. 12 is a view showing an example of an input interface display inthe system according to the invention;

FIG. 13 is a view showing another example of the input interface displayin the system according to the invention;

FIG. 14 is a view showing an example of an output interface display inthe system according to the invention;

FIG. 15 is a view showing an concrete example for illustratingestimation of a fraction defective in the assembling work fractiondefective estimating system according to the invention;

FIG. 16 is a view showing, by way of example, a computation model forarithmetically determining a assembling-related fraction defective;

FIG. 17 is a view showing, by way of example, a flow of operations in apart attaching work;

FIG. 18 is a view for illustrating an example of assembling work whichcan be completed by two types of attaching operations;

FIG. 19 is a view illustrating an arrangement of assembling workprocesses;

FIG. 20 is a view showing, by way of example only, display ofinformation and data outputted from a fraction defective estimatingsystem according to another embodiment of the present invention;

FIG. 21 is a view showing an example of database employed in thefraction defective estimating system according to another embodiment ofthe invention;

FIG. 22 is a view showing, by way of example, another database employedin the fraction defective estimating system according to anotherembodiment of the invention;

FIG. 23 is a view showing examples of the processing executed in thefraction defective estimating system according to another embodiment ofthe invention;

FIG. 24 is a view showing other examples of the processing executed inthe fraction defective estimating system according to the invention; and

FIG. 25 is a view showing formulae for estimatingpart-attachment-related fraction defectives.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be described in detail in conjunction withwhat is presently considered as preferred or typical embodiments thereofby reference to the drawings. In the following description, likereference characters designate like or corresponding parts throughoutthe several views. Also in the following description, it is to beunderstood that such terms as “horizontal”, “downward” and the like arewords of convenience and are not to be construed as limiting terms.

Now, referring to the drawings, description will be made of a processingfor estimating a fraction defective in an article assembling work(hereinafter also referred to as the assembling-related fractiondefective) which processing can be carried out with the aid of afraction defective estimating system according to an embodiment of thepresent invention.

FIG. 1 is a schematic block diagram showing generally and schematicallya system configuration of the fraction defective estimating system forestimating a fraction defective relating to an assembling work accordingto the teaching of the present invention.

Referring to FIG. 1, a computation system shown therein is generallycomprised of a fraction defective estimating system 10 according to aninstant embodiment of the invention and a design system 20 which in turnis composed of a two-dimensional CAD (computer aided design) system or athree-dimensional CAD system, a part information database for storinginformation concerning names of parts, part identifying (ID) numbers,materials, weights, unit prices, etc. and others.

The fraction defective estimating system 10 is composed of an input unit1 constituted by a keyboard, a mouse, a pen-input tablet, a storagemedium, an input facility connected to a network or the like, an outputunit 2 constituted by a display unit such as a display monitor, aprinter, an output facility connected to an external system via anetwork or the like, a computing apparatus 3 designed for executing theestimation procedure according to the present invention, and a storageunit (external storage unit) 4 for storing a variety of information usedfor arithmetically determining or calculating the fraction defectives.On the other hand, the computing apparatus 3 is comprised of a centralprocessing unit or CPU 32, a read-only memory or ROM 31 storing apredetermined program or programs, a random access memory or RAM 33 forstoring temporarily various data, an input/output interface 34, a busline 35 and others.

According to the teaching of the present invention incarnated in thefraction defective estimating system, a process or work for assembling aproduct or an assembled part or subassembly is represented by acombination of predefined standard attaching operations, to therebycalculate or compute a likelihood of occurrence of assembling failure(i.e., assembling-related fraction defective) by totalizing fractiondefective coefficients relevant or relating to the individual standardattaching operations, respectively. With a view to enhancing theaccuracy of the fraction defective estimation, the number of attachingoperations required for completing a given assembling work, conditionsrelating to the attachment-destined parts and attachment-subjected partssuch as the conditions e.g. by shapes, dimensional precisions, surfacestates, sizes, weights, materials, functions and the like, conditionsrelating to the assembling work-shops, and the presence or absence of aprocess for confirming the completed assemblage are employed assupplementary coefficients in computing the likelihood of occurrence ofassembling failure (fraction defective).

In other words, an object under evaluation is represented by acombination of standard attaching operations, wherein values obtained bycorrecting supplementarily the fraction defective coefficientspredetermined for the individual standard attaching operations,respectively, with the number of attaching operations, the conditionsgiven by the attachment-destined parts and the attachment-subjectedparts, respectively, the conditions imposed by the assembling work-shopand the presence or absence of the completed assemblage confirmingprocess are totalized, for thereby computing the fraction defective.

The reason why the fraction defective of the part attaching work isdetermined by taking into account the contents of operations involved inthe attaching work, the properties of the attachment-destined parts andthe attachment-subjected parts, the presence/absence of the process orstep of confirming whether the work has been completed properly orsatisfactorily and the conditions relating to the assembling work-shop,as described above, can be explained as follows.

Needless to say, any attaching operation is accompanied with thepossibility or potential of the assembling-related failure taking place.(Such potential is referred to as the assembling-related fractiondefective coefficient.) In this conjunction, it is noted that a majorfactor which affects primarily the defect occurrence likelihood can befound in the attaching operation.

As the factors increasing or decreasing the assembling-related fractiondefective coefficient in the attaching operation, there can be mentionedproperties or statuses of the attachment-destined part as well as theattachment-subjected part and the conditions of the work-shop or fieldwhere the attaching work is performed.

By way of example, with regards to the properties of theattachment-destined part and the attachment-subjected part, theassembling-related fraction defective coefficient of the attachingoperation is amplified or increased when the attachment-destined partand/or the attachment-subjected part have shapes which make it difficultto perform the attachment operation.

Similarly, the assembling-related fraction defective coefficient of theattaching operation is affected by the condition of the work-shop orfield where the assembling work is performed. By way of example, whenequipment employed for the assembling work is likely to producedefectives, the fraction defective coefficient of the attachingoperation will increase when compared with the case where the equipmentwhich is unlikely to produce the detective for a same assembling work.Furthermore, when the operation workers engaged in assembling work inthe assembling shop or field have high skill as a whole, the fractiondefective coefficient for a given attaching operation becomes a lowvalue when compared with the assembling shop where the workers are oflow skill.

Additionally, by providing as the defective detection potential thecheck process for confirming whether a given attaching work has beencompleted satisfactorily in succession to the attaching work process foran object for which of the assembling-related fraction defective is tobe estimated, occurrence of the defect can be detected in this checkprocess or step, whereon suitable measures for coping with the defectcan be taken. Thus, the probability of the assemblage becoming finallydefective can be lowered.

For the reasons mentioned above, in the fraction defective estimatingsystem according to the instant embodiment of the invention, thefraction defective is arithmetically determined or computed on the basisof the contents of operations involved in the attaching work, theproperties of the attachment-destined part and the attachment-subjectedpart, the presence or absence of the check process for confirmingwhether the attaching work has been completed as desired, and theconditions given by the work-shop where the attaching work is performed,since these represent factors which exert non-negligible influence tothe occurrence of the assembling failure.

To this end, the storage unit 4 is designed to store the coefficientscorresponding to the kinds or types of part attaching operations,coefficients relating or corresponding to the number of attachingoperations which are required for completing a given assembling work(also referred to as the number of attachments), coefficientscorresponding or relating to properties of the attachment-destined partand the attachment-subjected part (e.g. shape, dimensional precision,surface state, size, weight, material, function, etc.), coefficientcorresponding or relating to the provision of the process or step ofconfirming the completed assemblage in succession to the attaching work,coefficient corresponding or relating to the condition of the assemblingwork-shop where the assembling work is to be done, and the computationprogram(s) containing arithmetic expressions or formulae forarithmetically determining the fraction defective and executed by thefraction defective estimating system now under consideration. Thecoefficients stored in the database are so preset that they assume largevalues or alternatively small values for the items for which the defector failure is more likely to occur. Preferably, these coefficientsshould be determined in consideration of real data of the assemblingfailures which occurred really in the past.

In the computation program stored in the storage unit 4, there are usedthe assembling failure estimating formulae which are mentioned below:$\begin{matrix}{{{\begin{matrix}\text{Estimated~~value~~of~~assembling-related} \\{{fraction}\quad{defective}\quad\text{in~~part~~attaching~~work}}\end{matrix} = \begin{matrix}\begin{matrix}{{f1}\left( {\text{content~~of~~attaching~~operation,~~}\text{properties~~of~~parts,}} \right.} \\{{{conditions}\quad{given}\quad{by}\quad{work}\text{-}{shop}\quad{and}\quad{presence}\quad{or}}\quad}\end{matrix} \\{{\left. {{absence}\quad{of}\quad{check}\quad{process}} \right),}\quad}\end{matrix}}{or}}\quad} & (1) \\{\quad{= \begin{matrix}\begin{matrix}{{f2}\left( {\text{attachment-operation-based~~fraction~~}\text{defective~~coefficient,}}\quad \right.} \\{{{part}\text{-}{related}\quad{supplementary}\quad{coefficients}},{{shop}\text{-}{related}\quad{supplementary}\quad{coefficients}},}\end{matrix} \\{{\left. {{check}\text{-}{process}\text{-}{related}\quad{supplementary}\quad{coefficient}} \right),}\quad}\end{matrix}}} & (2)\end{matrix}$where f1( ) and f2( ) represent functions, respectively.

Thus, the likelihood of occurrence of failure in the part attaching workconstituted by a time series of three consecutive operations can bearithmetically determined by adding together the values obtained bycorrecting supplementarily the fraction defective coefficients of thefirst attaching operation, second attaching operation and the thirdattaching operation, respectively, with the part-related supplementarycoefficient, the shop-related supplementary coefficient and thecheck-process-related supplementary coefficient, as can be seen in FIG.11.

On the other hand, there can be conceived various methods for expressingin terms of formulae the supplementation of the individual operations byusing the part-related supplementary coefficients, shop-relatedsupplementary coefficient and the check-process-related supplementarycoefficient. By way of example, there may be mentioned a method ofmultiplying the attachment-operation-based fraction defectivecoefficient by the part-related supplementary coefficient, shop-relatedsupplementary coefficient and the check-process-related supplementarycoefficient, a method of subtracting or adding the part-relatedsupplementary coefficient, shop-related supplementary coefficient andthe check-process-related supplementary coefficient from or to theattachment-operation-based fraction defective coefficient or anexponential supplementing method.

Furthermore, as the supplementation method for the case where aplurality of part-related supplementary coefficients, shop-relatedsupplementary coefficients and the check-process-related supplementarycoefficients are present for a single attaching operation, there areconceivable a method of multiplying the attachment-operation-basedfraction defective coefficient relevant to the above-mentioned attachingoperation by all the part-related supplementary coefficients,shop-related supplementary coefficients and the check-process-relatedsupplementary coefficients, a method of adding (or subtracting) all ofthe part-related supplementary coefficients, shop-related supplementarycoefficients and the check-process-related supplementary coefficients to(or from) the attachment-operation-based fraction defective coefficientof that attaching operation.

For carrying out the present invention, there may be selected any one ofappropriate methods or procedures mentioned above so long as theattachment-operation-based fraction defective coefficient can besupplementarily corrected, i.e., supplemented, with the part-relatedsupplementary coefficient, shop-related supplementary coefficient andthe check-process-related supplementary coefficient. In thisconjunction, it should however be mentioned that theoperation-sequence-related supplementary coefficient, thecheck-process-related supplementary coefficient and the shop-relatedsupplementary coefficient (which may also be referred to as the shopconstants) are not necessarily required in carrying out the invention.

In the fraction defective estimating system now under consideration, theinformation (a to d) illustrated in FIG. 1 is inputted through the inputunit 1.

At first, information (a) representing a given attaching work with typesof previously prepared standard attaching operations as involved and thesequence thereof is inputted through the input unit 1. Morespecifically, symbols indicating preset standard attaching operationelements are inputted in accordance with a sequence in which theoperations involved in the attaching work are to be performed. FIG. 3Ashows some typical examples of the standard attaching operations and thesymbols indicating the operations, respectively, which may be inputtedto the fraction defective estimating system according to the invention.The standard attaching operations are selected as they are considered tobe necessary for representing or expressing the operations involved inrealizing a given part attaching work. In the case of the instantembodiment of invention, several types of standard attaching operationssuch as “downward movement”, “horizontal movement”, “insertion underpressure or press-fitting” and others are selected as the standardattaching operations. Among these preset standard attaching operations,the operation(s) which are involved in the given part attaching work andfor which the fraction defectives are to be estimated, respectively, areexpressed by using operation indicating symbols. By way of example, itis assumed that an attaching operation for a given part includes“downward displacement of the part which is followed by horizontaldisplacement of the part and finally press-fitting of the part”. In thatcase, the information which concerns the attaching operations for theassumed part attaching work and which is to be inputted can be expressedby the three standard attaching operation elements, i.e., downwardmovement, horizontal displacement and the press-fitting, and thus by asequence of operation symbols “↓→C”.

Subsequently, those conditions (b) are inputted which exert influence tothe uncertainty (defect occurrence likelihood) of the attaching workoperations for the attachment-destined parts and theattachment-subjected part in the attaching work of concern. By way ofexample, shape, dimensional precision, surface state, size, weight,material, function, etc. are inputted. More specifically, those factorswhich have influence to the degree of uncertainty of the attaching workoperations performed by a worker are selected from the properties of theattachment-destined parts and the attachment-subjected part, wherein thefactors thus determined are inputted in terms of symbols representingthese factors, respectively. Furthermore, characteristic of the factor(e.g. weight value) may be inputted when occasion requires. FIG. 3Bshows, by way of example, some of the part-condition-relatedsupplementary factors together with corresponding symbols in the systemaccording to the instant embodiment. In the case of the fractiondefective estimating system according to the instant embodiment, thereare preset several kinds of part-condition-related supplementary factorssuch as “fine hole”, “small hole”, “difficulty of confirming completedattachment (e.g. difficulty presented by shapes and properties of theattachment-destined parts and the attachment-subjected parts in decidingor confirming visibly, feelingly or audibly whether or not theattachment of the part has been completed)”, “presence of contactinhibiting surface (presence of a portion in the attachment-destinedpart or attachment-subjected part which is inhibited from beingcontacted from the standpoint of function and/or performance of theassembly)” and the like.

Next, the information (c) indicating presence or absence of the processfor confirming whether the attaching work has been completedsatisfactorily is inputted. As mentioned previously, the presence ofsuch confirmation process can contribute to lowering the likelihood ofoccurrence of the assembling failure which is determined by theattaching operations and the part conditions described above.

Inputted in succession is the information (d) concerning the factorshaving influence to the uncertainty of the operation involved inattaching the attachment-destined part to the attachment-subjected partin the attaching work. As the information (d), there may be mentionedthe condition imposed by the worker working in an assembling work-shop,conditions given by the equipment as used, environmental condition andso forth. In that case, information indicating the characteristics ofthe factors (e.g. temperature and humidity of the shop, production lot,production rate of a relevant production line, etc.) may be inputted asoccasion requires. According to the invention incarnated in the instantembodiment, the estimated value of the assembling-related fractiondefective is computed conveniently on a shop-by-shop basis by using anumerical value (shop constant) indicating the likelihood of occurrenceof the assembling failure on an average. With the shop constant, it iscontemplated to represent a multiple value indicating how large thefraction defective in a given shop is relative to the fraction defectivein a basic shop where a predetermined given assembling work (referred toas the basic work) is assumed to be performed. Although the shopconstant is inputted directly in the fraction defective estimatingsystem according to the instant embodiment of the invention, informationwhich can discriminatively identify a given shop may be inputted,provided that the shop constants are previously stored in the storageunit 241 (shop constant database) on a shop-by-shop basis.

At this juncture, it should be mentioned that the sequence or order inwhich the information is inputted is never restricted to that describedabove. To say in another way, the information may be inputted in anysequence as desired. Further, it should also be added that there mayexist some cases where the information (c) concerning the presence orabsence of the check process and/or the information (d) concerning theassembling shop conditions can be spared.

In the fraction defective estimating system now under consideration, theCPU 32 executes the computation program stored in the storage unit 4upon completion of the inputting operation of the information mentionedabove, to thereby extract the coefficients corresponding to the inputinformation from the storage unit 4 onto the RAM 33, whereon theestimated value of the assembling-related fraction defective in the partattaching work of concern is generated on the basis of the inputinformation in accordance with the formula (2) mentioned previously.

Now, internal processings executed internally by the fraction defectiveestimating system will be described in more detail by reference to afunctional block diagram shown in FIG. 2.

In the fraction defective estimating system 10 shown in FIG. 2, thecomputing apparatus 3 shown in FIG. 1 is composed of a data fetchingunit 34 for fetching design information and other from the design system20, a program executing unit 32 for executing the estimation processingtaught by the present invention, a computation program storage unit 31for storing a program or programs for the estimation processing taughtby the invention and an information generating unit 36 for generatingnew information on the basis of indications or commands displayed on thedisplay unit 2, while the storage unit 4 stores varies databases.Parenthetically, the program executing unit 32 may be so designed as toperform the function(s) of the information generating unit 36 as well.

Now, the contents of the various databases stored in the storage unit 4will be described below.

A standard-attaching-operation-based fraction defective coefficientdatabase 211 is adapted to store “standard-attachment-operation-basedfraction defective coefficients”, i.e., coefficients indicatinglikelihood of occurrence of work failure in each of the attachingoperations preset for each of the types of predetermined standardattaching operations such as e.g. “downward movement”, “horizontalmovement” and the like. FIG. 4 is a view illustrating examples of thedata of the standard-attaching-operation-based fraction defectivecoefficient database 211 in the fraction defective estimating systemaccording to the instant embodiment of the present invention. With thestandard attachment-operation-based fraction defective coefficient, itis contemplated to indicate a value of probability at which a workcarried out for each unitary standard attaching operation in the basicstate results in failure. The standard attachment-operation-basedfraction defective coefficient can be set relatively with reference to avalue of the probability of occurrence of the work failure in a givenattaching operation. In the case of the fraction defective estimatingsystem according to the instant embodiment of the invention, thefraction defective coefficients for the individual standard attachingoperations are previously established with reference to the “downwardmovement” which requires the simplest operation and for which theassembling work failure is difficult to occur. In more concrete, theattachment-operation-based fraction defective coefficient for “downwardmovement” is imparted with a basic value “1”, whereon multiplesindicating degrees of the likelihood of occurrence of failure in theother standard attaching operations, respectively, relative to the“downward movement” operation are set as the standardattachment-operation-based fraction defective coefficients for the otherstandard attaching operations, respectively. By way of example, theattachment-operation-based fraction defective coefficient for the“horizontal movement” is allocated with the value of “2” in the case ofthe data illustrated in FIG. 4, which means that the likelihood ofoccurrence of failure in the “horizontal movement” operation is twice aslarge as that in the “downward movement” operation.

The operation-sequence-related supplementary coefficient database 221stores “operation-sequence-related supplementary coefficients”, i.e.,the supplementary coefficients for increasing“attachment-operation-based fraction defective basic coefficient” foreach of individual attaching operations involved in a given attachingwork in dependence on the turns in the sequence of the attachingoperations because the work will become more complicated as the numberof operations involved in a given attaching work expressed by aplurality of standard attaching operation elements increases. FIG. 5shows, by way of example only, data of the operation-sequence-relatedsupplementary coefficients. As can be seen in FIG. 5, theoperation-sequence-related supplementary coefficients may be set independence on the turns in the operation sequence such that theoperation-sequence-related supplementary coefficient for the firstoperation is allocated with “1”, that for the second operation isallocated with “1.1”, the third operation is allocated with “1.2” and soforth. As an alternative, the operation-sequence-related supplementarycoefficient database 221 may be so designed as to contain a coefficientcalculating expression for calculating the operation-sequence-relatedsupplementary coefficients as a function of the turn of a concernedoperation in the operation sequence. By way of example, representing theoperation located at n-th turn in the operation sequence by n, thefollowing formulaoperation-sequence-related supplementary coefficient=n×1.1  (3)may be contained in the database as the data, for thereby determiningthe estimated value of the assembling-related fraction defective bytaking into account the operation-sequence-related supplementarycoefficient determined in accordance with the above formula (3) read outupon determination of the estimated value of the assembling-relatedfraction defective.

It is further noted that the likelihood of occurrence of the workfailure in the individual attaching operations is subjected to theinfluence of the conditions or states of the attachment-destined parts,the counterpart attachment-subjected part and the ambient conditionsthereof. For this reason, there is provided theattachment-destined-part-condition-related supplementary coefficientdatabase 231. More specifically, the likelihood of occurrence of thework failure in each of the attaching operations can vary as a functionof the properties of the attachment-destined part such as the size,weight, material, the number of positional alignments as required andthe like. Similarly, the above-mentioned likelihood varies in dependenceon the similar property conditions of the attachment-subjected part. Forthe reasons mentioned above, there are stored in theattachment-destined-part-condition-related supplementary coefficientdatabase 231 and the attachment-subjected-part-condition-relatedsupplementary coefficient database 232 the attachment-destined partproperty factors and the attachment-subjected part property factorswhich exert significant influence to the likelihood of occurrence in therespective attaching operations together with the part-condition-relatedsupplementary coefficients for supplementing the standardattachment-operation-based fraction defective coefficients on afactor-by-factor basis. FIG. 6 is a view illustrating examples of datain the attachment-destined-part-condition-related supplementarycoefficient database 231 and theattachment-subjected-part-condition-related supplementary coefficientdatabase 232. As can be seen in the figure, the supplementarycoefficient value is predetermined and stored for each of thesupplementary factors. As an alternative, theattachment-destined-part-condition-related supplementary coefficientdatabase 231 may be so designed as to contain a coefficient computingformula in place of the supplementary coefficient values, as in the caseof the operation-sequence-related supplementary coefficient database 221described hereinbefore. In that case, the above-mentioned formula isread out from the attachment-destined-part-condition-relatedsupplementary coefficient database 231 for calculating the estimatedvalue of the assembling-related fraction defective by taking intoaccount the supplementary coefficient determined in accordance with theformula as read out. Incidentally, theattachment-destined-part-condition-related supplementary coefficientdatabase 231 and the attachment-subjected-part-condition-relatedsupplementary coefficient database 232 may be implemented in themutually different structures.

As mentioned hereinbefore, the likelihood of occurrence of the workfailure in the individual attaching operations becomes differentremarkably in dependence on the conditions of the shops where theassembling work is performed. Accordingly, in the fraction defectiveestimating system according to the instant embodiment of the invention,the shop constant database 241 is provided, which is so designed as tostore the constants each indicating the likelihood of occurrence offailure on an average in each of the individual shops. In the case ofthe fraction defective estimating system according to the instantembodiment of the invention, the assembling-related fraction detectivesin carrying out the basic work (the downward movement in the case of theinstant embodiment) are set as the shop constants for the individualshops, respectively, on the presumption that the other conditions thanthe shop condition are in the basic state in the individual shops. FIG.7 is a view showing, by way of example, contents of the shop constantdatabase 241. As can be seen in the figure, a shop “A” has the shopconstant “5 ppm” with a shop “B” being allocated with a shop constant of“10 ppm”, which means that in the shop “A”, the fraction defective ofthe downward movement is 5 ppm with the fraction defective of thedownward movement being 10 ppm in the shop “B” on the assumption thatall the other conditions except for the shop condition are in the basicstate. Thus, it is safe to say that the shop constant represents anindex indicating real reliability of the assembling work in each of theshops. At this juncture, it should further be added that the shopconstant represents the constant which reflects influences ascribable tothe condition of the worker engaged in the assembling work in therelevant shop, equipment conditions such as those of tools/jigs,production line facilities, etc., environmental conditions of the shopsuch as temperature, humidity, illumination, noise, etc., productionconditions such as of production line speed, the number of productionlots and so forth.

As described above, when the process or step of checking whether or nota part attaching work of concern has been completed property after theattaching work of the part which is an object for the estimation ofassembling-related fraction defective, the fraction defective can belowered. To this end, the check-process-related supplementarycoefficient database 25 stores supplementary coefficients reflecting theeffects of such check process. FIG. 8 is a view showing examples of datain the check-process-related supplementary coefficient database 25. Ascan be seen in the figure, the check-process-related supplementarycoefficient having a value of “0.2” indicates that owing to the checkprocess, 80% of the assembling failures occurred in assembling works ofconcern can be discovered. In this conjunction, it is noted that in casethe ratio at which the failure can be discovered becomes different independence on the types of the checking works, the check-process-relatedsupplementary coefficient may be provided for each of the checkprocesses which differ from one another in respect to the content of thechecking work.

Further, an other-constants database 26 serves for storing otherconstants and other types of coefficients than those mentioned above.

An input-data/computed-data storage unit 27 serves for storing the inputdata used in the fraction defective computation by the computationprogram as well as the result of computations obtained by executing thecomputation program on the basis of the input data. Parenthetically, itshould be mentioned that the operation-sequence-related supplementarycoefficient database 221, the check-process-related supplementarycoefficient database 25 and the shop constant database 241 are notalways indispensably required.

It should further be added that the coefficients stored in therespective databases may be so set that the values of the supplementarycoefficients can change as the characteristic values of thesupplementary factors (e.g. weight value in the case of the weightfactor) change, as is illustrated in FIG. 10.

In more concrete, the supplementary coefficient may be so set as toassume a constant value in dependence on the content or type of thesupplementary factor regardless of the characteristic value of thesupplementary factor, as in the case of Example 1 shown in FIG. 10. (Assuch supplementary coefficient, there may be mentioned “completedattachment confirming difficulty”, “presence of contact inhibitingsurface” and the like.) In the case of Example 2 shown in FIG. 10, thevalue of the supplementary coefficient changes stepwise (e.g. formulti-point alignment). In the case of Example 3 shown in FIG. 10, thevalue of the supplementary coefficient changes linearly (e.g. when thesupplementary coefficient concerns weight). Of course, the supplementarycoefficient may be changed curvilinearly as occasion requires. In thiscase, the coefficients are arithmetically determined on the basis ofappropriate one of the functions such as illustrated in FIG. 10 inresponse to the inputting of the characteristic value as required.

FIG. 9 shows a flow chart for illustrating a procedure for computing theestimated value of the assembling-related fraction defective in a partattaching work, which procedure is executed by the fraction defectiveestimating system according to the instant embodiment of the invention.

At first, the content of the part attaching work for which the fractiondefective is to be estimated is analyzed (step 5).

Subsequently, the content of the analysis performed in the step 5 isexpressed by using the standard attaching operation element symbol(s)and the part-related supplementary element symbol(s) which arepredetermined in conjunction with the assembling fraction defectiveestimated value computation program designed to be executed by thefraction defective estimating system 10 (step 6).

In succession, the content of the part attaching work for the object forestimation of the assembling-related fraction defective expressed interms of the standard attaching operation element symbol(s) and thepart-related supplementary element symbol(s) in the step 6 mentionedabove are inputted. Additionally, the presence or absence of the checkprocess and the shop constant(s) are inputted as well (step 7).

In this way, after having put into operation the fraction defectiveestimating system 10, the assembling fraction defective estimated valuecomputation program stored in the computation program storage unit 31incorporated in the computing apparatus 3 is activated, whereon theinformation shown in FIG. 1 is inputted with the aid of the keyboard 11,the mouse 12 and/or the pen-input tablet 13 which constitutes a part ofthe input unit 1. In the case of the fraction defective estimatingsystem-according to the instant embodiment of the invention, an inputinterface menu is displayed on a display unit 21 constituting a part ofthe output unit 2, so that the operator can input the informationmentioned above while viewing the input interface menu as displayed. Byvirtue of this arrangement, the information input operation can befacilitated. FIGS. 12 and 13 show typical examples of such inputinterface menu. Further, in case the check process for confirmingwhether or not the attaching work has been properly exists, inputinformation indicating “presence of check process” is inputted as well.Additionally, the shop constant of a shop where the part attaching workwhich is the object for estimation of the assembling-related fractiondefective is performed or alternatively information specifying theassembling shop of concern is also inputted. Needless to say, unlesssupplementation for the part is necessary, the part-relatedsupplementary element symbol need not be inputted.

By the way, in the fraction defective estimating system according to theinstant embodiment of the invention, the shop constant can be computedin such a manner as described below. At this juncture, it should berecalled that in the fraction defective estimating system nowconsideration, the shop constant represents the assembling-relatedfraction defective in the case where the work only for the downwardmovement operation is performed in the state in which no partsupplementing conditions to be taken into account exists in the shop ofconcern. Additionally, all the attachment-operation-based fractiondefective coefficients are defined with reference to the likelihood ofoccurrence of failure when the basic operation (operation for downwardmovement) is carried out in the basic state. (In this case, thecoefficient value is allocated with a value of “1”.) The same holdssubstantially true for the supplementary coefficients for supplementingthe attachment-operation-based fraction defective coefficients. In otherwords, the supplementary coefficient is defined with reference to thelikelihood of occurrence of failure in the basic operation (downwardmovement) in the basic state. (In that case, the supplementarycoefficient is also allocated with the basic value of “1”.) For thesereasons, the contents of the assembling work which was really carriedout a number of times in the past can be analytically examined, tothereby compute the shop constant on the basis of the real fractiondefective data for the shop where the assembling work was reallyperformed in the past. In the fraction defective estimating system nowunder consideration, after the assembling fraction defective estimatedvalue computation program has been activated, a menu is generated on thedisplay unit 21 of the input unit 1 to thereby allow the operator toselect either “estimation of assembling-related fraction defective” oralternatively “computation/registration of shop constant”. When“computation/registration of shop constant” is selected, an inputinterface menu illustrated in FIG. 13 is displayed on the display unit21 of the input unit 1, whereon a code (name, identifier or the like)for specifying a shop to be registered is inputted, which is thenfollowed by inputting of the content of the assembling work reallycarried out in the specified shop in terms of the standard attachingoperation element symbols and the part-related supplementary elementsymbols in accordance with prompting indicated in the input interfacemenu (FIG. 12). Subsequently, in case the check process for confirmingwhether or not the attaching work has been carried out properly exists,the information indicating “check process exists” is inputted. Inaddition, the real fraction defective of the work concerned is alsoinputted. Thus, the shop constant of the shop of concern can becomputed. In case there exist a plurality of works for which the failurehas really occurred in the past, the aforementioned data concerning allof these works are inputted for thereby allowing the shop constant to bedetermined for each of these works, whereon the shop constant of theshop of concern can be arithmetically determined by resorting to amethod of determining a simple means of the shop constants as obtained.In the case of the fraction defective estimating system now underconsideration, it is presumed that the shop constant of the shop ofconcern is determined by calculating a simple means of the shopconstants as obtained.

Upon completion of the inputting procedure described above, theestimated value of the fraction defective in the part attaching work ofconcern is determined in a step 8 by executing the assembling-relatedfraction defective value estimating computation program on the basis ofthe information inputted in the step 7 mentioned above (step 8). Morespecifically, processings (1) and (2) described below are performed tothis end.

-   (1) Various coefficients/constants mentioned below are read out from    the various databases on the basis of the input information    mentioned above.

The fraction defective coefficients for the individual attachingoperations are read out from the standard-attaching-operation-basedfraction defective coefficient database 211 on the basis of the standardattaching operation element symbols inputted as mentioned previously.Further, the operation-sequence-related supplementary coefficientsconforming to the sequential order of operations are read out from theoperation-sequence-related supplementary coefficient database 221.

The part-condition-related supplementary coefficients for the individualsupplementary elements are read out from theattachment-destined-part-condition-related supplementary coefficientdatabase 231 or the attachment-subjected-part-condition-relatedsupplementary coefficient database 232 on the basis of thepart-condition-related supplementary element symbols inputted asmentioned previously.

In case the information “check process exists” has been inputted,corresponding check-process-related supplementary coefficients are readout from the check-process-related supplementary coefficient database25.

In case the information specifying the assembling shop has beeninputted, the shop constant of the shop of concern is read out from theshop constant database 241.

-   (2) A computation model is generated. Computation formulae are    generated in accordance with the computation model shown in FIG. 11    on the basis of the various coefficients/constants inputted or read    out as described previously. In that case, information concerning    the supplementing methods based on the various supplementary    coefficients, e.g. method resorting to multiplication of the    supplementary coefficients, addition or subtraction thereof, may be    registered for each of the supplementary factors in the various    supplementary coefficient database or alternatively the computation    program may be so programmed that the supplementing method is    changed in dependence on the types of the supplementary factors. In    the fraction defective estimating system now under consideration, it    is presumed that the computation program is programmed to change the    supplementing method in dependence on the types of the supplementary    factors. To this end, creation of the program as well as    determination of the coefficient values is realized, for example, on    the basis of a rule to the effect that all the supplementary    coefficients are added. Thus, according to the teachings of the    invention incarnated in the instant embodiment, the fraction    defective coefficient for a given operation is supplemented with the    part-condition-related supplementary coefficient for supplementing    that given operation in each operation sequence. Of course, no    supplementation is performed unless the supplementary factor is    available. Subsequently, all the supplemented fraction defective    coefficients are added together in each operation sequence. In case    the information “check process exists”, the sum obtained is then    multiplied with a check-process-related supplementary coefficient to    thereby determine arithmetically a totalized or overall fraction    defective coefficient which is then multiplied by the shop constant.    In this way, the estimated value of the assembling-related fraction    defective of the part attaching work of concern in the shop as    specified can be arithmetically determined.

In succession, the estimated value of the assembling-related fractiondefective computed in the step 8 mentioned above is outputted to thedisplay unit 21 or a printer unit 22 of the output unit 2 oralternatively to an output unit 23 of other system (step 9). An exampleof the information outputted to the display unit 21 is illustrated inFIG. 14.

Through the procedure described above, the estimated value of theassembling-related fraction defective for the part attaching work can bearithmetically determined by the system according to the instantembodiment of the invention. Although the foregoing description isdirected, by way of example, to the arithmetic determination of theestimated value of the assembling-related fraction defective for theattaching work in a single attaching work process, it should beunderstood that the estimated value of the assembling-related fractiondefective can be arithmetically determined for the whole assembling workof an article or product by inputting the information concerning theattaching operations and/or the information concerning thepart-condition-related supplementary elements mentioned previously forthe individual work processes, respectively, which are included in theassembling work of the article, for thereby calculating the estimatedvalues of the assembling-related fraction defectives for the individualwork processes, respectively, and totalizing the estimated values of theassembling-related fraction defectives as obtained.

Parenthetically, the information concerning the presence or absence ofthe check process is not always needed. The fraction defective asdesired can be calculated even when this information is absent. Itshould also be mentioned that the above-mentioned information can bespared so far as the shop constant is preset.

Again referring to the flow chart shown in FIG. 9, description will bedirected to a method of computing the estimated value of theassembling-related fraction defective in the part attaching work bytaking as example a concrete part attaching work (work involved inattaching a connector cable) shown in FIG. 15. Parenthetically, a tableshown in a lower part of FIG. 15 can be generated as an input/outputinterface image, wherein items to be analyzed are displayed in an inputcolumn. In the case of the example now under consideration, afteractivation of an assembling-related fraction defective value estimatingcomputation program, the work for evaluation can be analyzed whileviewing the input/output interface image, whereon input the results ofthe analyses can be inputted.

The analysis of the part attaching work now under consideration (step 5)shows that the connector cable attaching work for which theassembling-related fraction defective is to be estimated is composed oftwo works or processes mentioned below.

-   (1) Insertion of the Connector with a Large Inserting Force.-   (2) Deforming of the Cable.

Further, the conditions of the attachment-destined part as well as theconditions of the attachment-subjected part in the respective works areanalyzed. To this end, the analysis is performed for the item(s) enteredin the input column of the input/output interface image. At first,concerning the work “insertion of connector with large inserting force”,it is analytically determined that the condition of theattachment-subjected part is “fine hole” because of “fine-pinconnector”. Further, “completed attachment confirming difficulty, i.e.,it is difficult to decide whether or not the attachment has beencompleted” is decided because of “impossibility of visual confirmationof attachment-completed state due to presence of obstacle”. Concerningthe work (2) “deforming of cable”, there exists no part condition to besupplemented.

Subsequently, the work determined analytically in the step 5 isexpressed by using the standard attaching operation element symbol andthe part-related supplementary element symbol (step 6). At first, theattaching work is expressed in terms of the standard attaching operationelement symbol, whereon the part-condition-related supplementary elementsymbols are allocated to the operation elements on a one-by-one basis.In the case of the example shown in FIG. 15, the work is expressed asfollows.

-   (1) The work “insertion of connector with large inserting force” is    expressed by standard attaching operation elements “horizontal    movement (symbol: ←)” and then “insertion under pressure (symbol:    C)”. In other words, the first operation is “horizontal movement    (symbol: ←)” and the second operation is “insertion under pressure    (symbol: C)”.

Subsequently, the part-condition-related supplementary element for thefirst work “horizontal movement (symbol: ←)” is expressed by “fine hole(symbol: ht)”. Further, because of the part-condition-relatedsupplementary element of the “insertion under pressure (symbol: C)” isexpressed by “completed assemblage confirming difficulty (symbol: ?)”.For the second operation, there is required operation sequencesupplementation, which is automatically performed in accordance with thecomputation program in the fraction defective estimating system nowunder consideration.

-   (2) The standard attaching operation element “deforming of cable” is    expressed as “deforming (symbol: d)”. However, the    part-condition-related supplementary element of this operation need    not be expressed because there is any other element than the    operation-sequence related supplementation. Further, because this    operation is the third operation, the operation-sequence related    supplementation can be automatically performed in accordance with    the check process.

Next, the element symbols generated in the step 6 are inputted to theassembling-related fraction defective value estimating computationprogram, i.e., program for computing an estimated value of the fractiondefective in assembling, in a step 7. By way of example, names of theattachment-destined parts are entered in the part name column and thenthe standard attaching operation elements and the part-condition-relatedsupplementary elements are entered on a line-by-line basis for eachoperation included in the operation sequence, as is illustrated in FIG.15.

In more concrete, in the case of the example shown in FIG. 15, thestandard attaching operation element symbol “←” for the first operationin the operation sequence is inputted, whereon thepart-condition-related supplementary element “ht” for that operation isentered in the attachment-subjected part condition column “finehole/tight hole”. Subsequently, in the second line, the standardattaching operation element symbol “C” for the second operation in theoperation sequence is inputted, whereon the part-condition-relatedsupplementary element symbol “?” for that operation is entered in theattachment-subjected part condition column “completed attachmentconfirmation”. Then, in the third line, the standard attaching operationelement symbol “d” for the third operation in the operation sequence isinputted. Concerning this operation, no part-condition-relatedsupplementary element is inputted because such supplementary elementdoes not exist.

Since there is no check process for confirming whether the attachingwork of concern has been performed or not, no information is inputtedconcerning the “check process”.

Further, when the shop constant of the shop evaluation is stored in thedatabase, the shop to be evaluated is also inputted. In the case of theexample illustrated in FIG. 15, it is assumed that the shop name “A” isinputted. It should further be added that when the shop constant of theshop which can be regarded as being similar to the shop of concern, theformer can be inputted. Besides, in case the shop constant is known, itcan be directly entered in the shop constant input column.

Now, automatic computation is carried out by executing theassembling-related fraction defective value estimating computationprogram (step 8). To this end, the coefficient values corresponding,respectively, to the individual symbols entered in the input column inthe input/output interface image are read out from the variousdatabases, and the fraction defective coefficient indicating thelikelihood of occurrence of failure in the operation is arithmeticallydetermined for each of the operations on the basis of the coefficientvalues read out from the databases. For instance, the fraction defectivecoefficient is computed by using expressions 4 or 5 shown in FIG. 25.

As can be seen from the input/output interface image shown in FIG. 15,the fraction defective coefficients are arithmetically determined forthe operations, respectively, wherein total sum of the fractiondefective coefficients represents the fraction defective coefficientindicating the likelihood of occurrence of failure in the connectorcable attaching work and having a value of “30”. On the other hand, theshop constant of the shop “A” is read out from the shop constantdatabase 241, and the fraction defective coefficient mentioned above ismultiplied by the shop constant to thereby determine the estimated valueof the assembling-related fraction defective for the work of concern inthe shop “A”. In the case of the illustrated example, the shop constantof the shop “A” is “5 ppm”, and thus the estimated fraction defective inthat shop “A” is “150 ppm”.

Incidentally, reading of the coefficient values from the variousdatabase may be carried out when the assembling-related fractiondefective value estimating computation program is activated and storedin the RAM 33. In that case, the individual coefficient values are readout from the RAM 33 upon every computation, making it unnecessary toaccess the external storage unit, as a result of which the time involvedin the computing operation can be shortened, to an advantage.

The result of the computation of the estimated value of theassembling-related fraction defective as carried out by the fractiondefective estimating system 10 in accordance with the assembling-relatedfraction defective value estimating computation program is outputted(step 9).

It is noted in conjunction with the example illustrated in FIG. 15,types or species of parts can be inputted as the conditions of theattachment-destined part and the attachment-subjected part,respectively, the reason for which can be explained as follows.

The assembling failure may be roughly classified into two categories,i.e., imperfect assembly and injury/soil of part.

The “imperfect assembly” is primarily attributable to inaccurateoperation (deviation of the operation accuracy) and error of a worker inthe work. In the case of the connector attaching work, there may bementioned “imperfect insertion (state in which cable is not inserted tofull depth)”, “insertion of connector in horizontally reversedorientation” and the like.

On the other hand, the “injury/soil of part” may occur as a result ofdeviation of operation (dispersion of operation accuracy) and/or errorbrought about by the worker. However, the part suffering “injury/soil ofpart” can not always be regarded as the defective but it depends on thetype of the part even the “injury/soil of part” is same. By way ofexample, design parts which are exposed in outer appearance of anassembly represent such type of part which may well be considered asdefective in case there exists even a bit of injury and/or soil. To sayin another way, parts undergone an external force (stress) of samemagnitude can not always be regarded as defective. Rather, it may dependon the part species or types, i.e., functions or roles imparted to theparts.

For the reason mentioned above, the coefficient values indicatingstrengths (withstanding capabilities) of individual parts againstexternal force are stored in the database for each type of the part forthereby making it possible to input the part species or types of theattachment-destined parts and the attachment-subjected parts so that theestimated fraction defective can be arithmetically determined by takinginto account the probability of “injury/soil of part” defect bycomparing the strength (withstanding capability) of a part forevaluation with magnitude of the external force (stress) acting on thatpart upon attaching operation thereof. In this way, in the fractiondefective estimating system according to the instant embodiment of theinvention, not only the defect due to “imperfect assembly” but alsospoil due to “injury/soil of part” can be taken into account in theestimation of the fraction defective.

Next, description will be directed to the fraction defective estimatingsystem according to another embodiment of the present invention.

Basically, a working operation may be considered as repetition of“positioning operation” and “post-positioning operation. FIG. 17 showsan example of an attaching work which can be completed through a singleattaching operation “work for insertion of a part into a round holeformed in a cylinder through downward movement”. As can be seen fromFIG. 17, although the work illustrated therein is “operation fordownward movement”, the contents of which are, however, “positioningoperation” and “post-positioning operation”. Further, FIG. 18 is a viewillustrating, by way of example, an attaching work “cover mounting work”which can be completed by two types of attaching operations. This workis composed of two operation processes, i.e., “oblique-downwardmovement” process and “rotational movement” process, wherein standardoperations involved in each of these processes are “positioningoperation” and “post-positioning operation”.

There are some of the standard operations which can be completed throughonly one operation “positioning operation” such as operation for holdinga part or operation for shaping an electric conductor. However, many ofoperations are each achieved by a combination of “positioning operation”and succeeding “post-positioning operation”. FIG. 19 is a viewillustrating, by way of example, an arrangement of a work process.Referring to the figure, an attaching work of a part “1” in a process orstep “1” is constituted by three operations (first to third operations“1”, “2” and “3”), wherein each of the operations “1”, “2” and “3” isrealized by repeating “positioning” and “post-positioning operation”.

As will now be understood, the work is generally constituted by“positioning” and “post-positioning operation”. Consequently, the workfailures can roughly be classified into two types, i.e., work failuresoccurring in the positioning operation and work failures occurring inthe post-positioning operation, which has been experimentallyestablished by the inventors in the course of studies and experiments indeveloping the fraction defective estimating technique.

Firstly, the failure or defect occurring in the positioning operation isascribable to dispersion (inaccuracy) of the positions or postures ofparts in the positioning operation. When the attachment process transitsto the intrinsic operation with inadequate positioning, not only such afailure may occur that the intrinsic operation is rendered impossible(incomplete-work failure) but also such situation may be incurred that acoupled or bonded or connected portion between the attachment-destinedpart and the attachment-subjected part is injured or deformed due to aforce exerted in the intrinsic operation although it depends on thestrength of such coupled portion. Ordinarily, a worker makes transitionto a post-positioning operation after having confirmed that thepositioning is proper. If the positioning is improper, he or shecorrects the positioning before starting the intrinsic operation orpost-positioning operation. However, when difficulty is encountered inconfirming the positioning due to less-visibility of the relevantlocation or when the confirmation of the positioning is omittedunintentionally, the failures such as mentioned above are likely tooccur.

On the other hand, the assembling failures ascribable to thepost-positioning operation may be classified into failures due to pathcontrol failure in the post-positioning operation, i.e., deviation orinaccuracy of a path along which the part is moved for attachment andfailures due to insufficient operative effort. The assembling failuredue to the path control failure in the post-positioning operation islikely to occur with a high frequency when the part has to be movedalong a predetermined path over an extended distance among others. Onthe other hand, the assembling failure ascribable to insufficient of theoperative effort applied in the post-positioning operation will occurwhen the operative effort required for the attachment work can not beobtained. By way of example, when a large magnitude of the operativeeffort or force is required as in the case of insertion operation underpressure or press-fitting, the assembling failure mentioned just aboveis likely to occur if the operative effort or force of a predeterminedmagnitude can not be applied due to restriction imposed in view ofproperties of the part of concern and operation thereof.

The second embodiment of the present invention is directed a fractiondefective estimating system which is suited for evaluating occurrencepotentials of the faults such as mentioned above.

The system according to the instant embodiment of the invention isimplemented in a substantially same structure as the fraction defectiveestimating system of the first embodiment described hereinbefore(FIG. 1) except for differences in the information stored in thestandard-attaching-operation-based fraction defective coefficientdatabase 211 and the attachment-destined-part-condition-relatedsupplementary coefficient database 231 and the computation program forhandling the information.

FIG. 21 is a view illustrating the information to be stored in thestandard-attaching-operation-based fraction defective coefficientdatabase 211. The information now under consideration has featuresmentioned below.

A first feature can be seen in that three kinds of fraction defectivecoefficients, i.e., positioning-failure-ascribable fraction defectivecoefficient, path-control-failure-ascribable fraction defectivecoefficient and operative-effort-insufficiency-ascribable failurefraction defective coefficient are set for one standard attachingoperation. A second feature resides in that a standard attachingoperation is subclassified into two sorts of operations, i.e., theoperation for which higher accuracy exceeding a given reference isrequired and the operation which is free of such precision requirement.By way of example, the downward movement may include such downwardmovement for which high positioning accuracy is required and such sortof downward movement which is free of such positioning requirement.According to the teachings of the invention incarnated in the embodimentnow under consideration, the positioning-failure-ascribable fractiondefective coefficient is set to different values for the two sorts ofdownward movements mentioned above. Parenthetically, in the case of theexample illustrated in FIG. 21, the positioning fraction defectivecoefficients are set with reference to the basic positioning fractiondefective coefficient set to “1” (reference) for “the positioningdownward movement requiring high accuracy”. To say in another way,multiples indicating how many times high likelihoods of occurrence offailure are expected for the downward movements relative to thepositioning failure occurrence potential of “downward movement for thepositioning requiring high accuracy”.

On the other hand, FIG. 22 shows information to be stored in theattachment-destined-part-condition-related supplementary coefficientdatabase 231 and the attachment-subjected part-condition-relatedsupplementary coefficient database 232. To this end, three kinds ofsupplementary coefficient values are set for each of the supplementaryfactors as in the case of the information to be stored in thestandard-attaching-operation-based fraction defective coefficientdatabase 211.

Further, the computation program designed for handling the informationmentioned above exhibits features mentioned below. As describedpreviously, the path control failure occurrence potential of thepost-positioning operation and the operative-effort-insufficiencyfailure occurrence potential of post-positioning operation become highparticularly under some limited supplementary conditions. Accordingly,the computation program employed in the fraction defective estimatingsystem according to the instant embodiment of the invention is sodesigned as to compute the path control failure occurrence potential orthe operative-effort-insufficiency failure occurrence potential onlywhen given specific supplementary element is added to the operationincluded in the work under evaluation. More specifically, for theoperation added with the supplementary element indicating anover-extended-distance covering operation, i.e., operation over anextended distance, the path control failure occurrence potential isarithmetically determined in addition to the positioning failureoccurrence potential, whereas for the operation added with thesupplementary element indicating a large operative effort, theoperative-effort-insufficiency failure occurrence potential is computedin addition to the positioning failure occurrence potential. In otherwords, in dependence on the type of the supplementary element added toan attaching operation, decision is made as to whether or not thisoperation has the path control failure occurrence potential or theoperative-effort-insufficiency failure occurrence potential in additionto the positioning failure occurrence potential, to thereby executecomputation for determining the path control failure occurrencepotential or the operative-effort-insufficiency failure occurrencepotential in addition to the positioning failure occurrence potential asoccasion requires.

Now, description will turn to a method of computing an estimated valueof the assembling-related fraction defective in a part attaching work bytaking as example a part attaching work in the concrete by reference toFIGS. 23 and 24. In the examples (1) to (4) illustrated in FIGS. 23 and24, such work is presumed in which a cylindrical attachment-destinedpart having a diameter a is to be inserted into a round hole, whereinthe conditions under which the attachment-subjected part lies arechanged from one to another example. In more concrete, in the case ofthe example (1), a downward movement for which high accuracy ofpositioning is required because an insertion guide of the round holerepresenting the attachment-subjected part is small (i.e., outerdiameter of a chamfered portion of the round hole is small). On theother hand, in the case of the example (2), it is presumed that theinserting guide of the round hole representing the attachment-subjectedpart has a large diameter (having a chamfered portion of a large outerdiameter) and thus high precision or accuracy is not required for thepositioning. In other words, a downward movement work can be performedwithout need for paying especial attention to the work. Further, in theexample (3), a downward movement for which high accuracy of positioningis required because an insertion guide of the round hole representingthe attachment-subjected part has a small outer diameter at thechamfered portion of the round hole and additionally this downwardmovement work is required to be performed over an extended distancebecause the round hole is deep. Furthermore, in the case of the example(4), it is presumed that the inserting guide of the round holerepresenting the attachment-subjected part has a large diameter (havinga chamfered portion of a large outer diameter) and thus high accuracy isnot required for the positioning. Consequently, a downward movement workcan be performed without need for paying especial attention to the work.However, in this downward movement work, a large inserting force isrequired since a tight fitting work is required because of smallclearance between the diameter a of the attachment-destined part and thehole diameter c of the attachment-subjected part. At first, descriptionwill be made of methods for arithmetically determining the fractiondefective coefficients indicating failure occurrence potential in theassembling works shown as the examples (1) to (4), respectively, inFIGS. 23 and 24. In this conjunction, it is assumed that no checkprocess is performed in these exemplary works (1) to (4).

Firstly, the work exemplified at (1) in FIG. 23 is realized by adownward movement for which high positioning accuracy is required.However, there are no supplementary elements indicating the operationover an extended distance and a large operative effort. Accordingly, thework analysis will result in “downward movement for positioning”expressed by a symbol “↓′”. Upon inputting of the result of this workanalysis, the relevant positioning-failure-ascribable fraction defectivecoefficient is read out from the standard-attaching-operation-basedfraction defective coefficient database 211. In this case, thepositioning-failure-ascribable fraction defective coefficient willassume a value “1” because of “downward movement for positioning”(symbol: “↓′”) from the definition shown in FIG. 21. Besides, becausethe supplementary elements indicating the operation over an extendeddistance and the operation requiring a large operative effort are notinputted, neither the path-control-failure-ascribable fraction defectivecoefficient nor the operative-effort-insufficiency-ascribable failurefraction defective coefficient need not be determined. Thus, thetotalized or overall fraction defective coefficient for the work (1)shown in FIG. 23 is “1” in total. A practical fraction defective can beobtained by multiplying this fraction defective coefficient “1” by ashop constant inputted in advance.

Next, the work exemplified at (2) in FIG. 23 is realized by a downwardmovement for which positioning accuracy is not required because of alarge diameter of the insertion guide. However, there are nosupplementary elements indicating operation over an extended distanceand a large operative effort. Accordingly, the work analysis will resultin a simple “downward movement” expressed by a symbol “↓”. Uponinputting of this work analysis result, the relevantpositioning-failure-ascribable fraction defective coefficient is readout from the standard-attaching-operation-based fraction defectivecoefficient database 211. In this case, thepositioning-failure-ascribable fraction defective coefficient willassume a value “0.1” because of “downward movement” (symbol: “↓”) fromthe definitions shown in FIG. 21. Besides, because the supplementaryelements indicating the operation over an extended distance and theoperation requiring a large operative effort are not inputted, neitherthe path-control-failure-ascribable fraction defective coefficient northe operative-effort-insufficiency-ascribable failure fraction defectivecoefficient need not be determined. Thus, the overall fraction defectivecoefficient of the work (2) shown in FIG. 23 is “0.1” in total. Apractical fraction defective can be obtained by multiplying thisfraction defective coefficient “0.1” by a shop constant inputted inadvance.

The work exemplified at (3) in FIG. 24 is realized by a downwardmovement for which high positioning accuracy is required because of asmall diameter of the insertion guide. Accordingly, the work analysiswill result in “downward movement for positioning” expressed by a symbol“↓′” with the supplementary element being “over-extended-distanceinsertion” (symbol: lh). Upon inputting of this work analysis result,the relevant positioning-failure-ascribable fraction defectivecoefficient is read out from the standard-attaching-operation-basedfraction defective coefficient database 211. In this case, thepositioning-failure-ascribable fraction defective coefficient willassume a value “1” because of “downward movement for positioning”(symbol: “↓′”) in view of the definitions shown in FIG. 21. Further, inthis case, since the supplementary element indicating theover-extended-distance insertion is inputted, the positioning failuresupplementary coefficient “1” for the over-extended-distance insertionis read out from the attachment-subjected-part-condition-relatedsupplementary coefficient database 232 (see FIG. 22). Additionally,because of the over-extended-distance insertion, thepath-control-failure-ascribable fraction defective coefficient isarithmetically determined. To this end, thepath-control-failure-ascribable fraction defective coefficient “1” isread out from the standard-attaching-operation-based fraction defectivecoefficient database 211 (see FIG. 21). Subsequently, thepath-control-failure-ascribable fraction defective coefficient “2” forthe supplementation relating to the over-extended-distance insertion isread out from the attachment-subjected-part-condition-relatedsupplementary coefficient database 232 (see FIG. 22). Since thesupplementary elements indicating the operation requiring a largeoperative effort is not inputted in this case, theoperative-effort-insufficiency-ascribable failure fraction defectivecoefficient need not be determined. Thus, the overall fraction defectivecoefficient of the work (3) shown in FIG. 24 is “3” in total because thepositioning-failure-ascribable fraction defective coefficient is “1”(=1×1)” and because the path-control-failure-ascribable fractiondefective coefficient is “2” (=1×2)” and thus “3” in total. A practicalfraction defective can be obtained by multiplying this fractiondefective coefficient “3” by a shop constant inputted in advance.

Finally, the work shown at (4) in FIG. 24 is considered. Since it ispresumed that the insertion guide has a large diameter, the requirementfor positioning accuracy may be put outside of consideration. Further,because the work analysis will simply result in “downward movement”expressed by a symbol “↓” because of the absence of supplementaryelement. However, in view of the supplementary condition “tight fitting”represented by a symbol “th”, the work now under consideration can beanalytically expressed by operation “downward movement” (symbol: “↓”)and supplementary element “tight fitting” (symbol: “th”). Upon inputtingof the results of the work analysis, the relevantpositioning-failure-ascribable fraction defective coefficient is readout from the standard-attaching-operation-based fraction defectivecoefficient database 211. In this case, thepositioning-failure-ascribable fraction defective coefficient willassume a value “0.1” because of “downward movement” (symbol: “↓”) inview of the definitions shown in FIG. 21. Further, in this case, sincethe supplementary element “tight fitting” is inputted, the positioningfailure supplementary coefficient “1” for the “tight fitting” is readout from the attachment-subjected-part-condition-related supplementarycoefficient database 232 (see FIG. 22). Additionally, because of “tightfitting”, i.e., operation for which large operative effort is demanded,the operative-effort-insufficiency-ascribable failure fraction defectivecoefficient is arithmetically determined. To this end, theoperative-effort-insufficiency-ascribable failure fraction defectivecoefficient “1” is read out from the standard-attaching-operation-basedfraction defective coefficient database 211 (see FIG. 21). Subsequently,the operative-effort-insufficiency-ascribable failure fraction defectivecoefficient “5” for supplementation in view of the “tight fitting” isread out from the attachment-subjected part-condition-relatedsupplementary coefficient-database 232 (see FIG. 22). Since thesupplementary element indicating the operation over an extended distanceis not inputted, the path-control-failure-ascribable fraction defectivecoefficient need not be determined. Thus, the fraction defectivecoefficient of the work (4) shown in FIG. 24 is “5.1” in total becausethe positioning-failure-ascribable fraction defective coefficient is“0.1” (=0.1×1)” and because theoperative-effort-insufficiency-ascribable failure fraction defectivecoefficient is “5” (=1×5)”. A practical fraction defective can beobtained by multiplying this fraction defective coefficient “5.1” by ashop constant inputted in advance.

FIG. 20 is a view showing, by way of example only, the fractiondefective coefficients for the positioning failure, the path controlfailure and the operative-effort-insufficiency-ascribable failure,respectively, which can be outputted from the system according to thesecond embodiment of the invention.

As will now be understood from the foregoing, according to the teachingof the present invention incarnated in the second embodiment, it ispossible to estimate the fraction defectives finely by taking intoconsideration the occurrence potential for each of the positioningfailure, the path control failure and the operative effortinsufficiency, whereby the accuracy in estimating the fractiondefectives can be significantly enhanced, to an advantage. Furthermore,because the occurrence potentials of the positioning failure, the pathcontrol failure and the operation effort insufficiency, respectively,are outputted, it is possible to determine quantitatively which of theoperations involved in the work under evaluation has what degree offailure potential. Thus, in the stage of design preceding to theassembling for which estimation of the fraction defective is performedaccording to the teaching of the invention, information concerningimprovements to be done can be made available. Besides, the failureevents or phenomena can also be predicted on the basis of combinationsof levels of the occurrence potentials and the part-condition-relatedsupplementary coefficients of various types.

As is apparent from the foregoing description, according to theteachings of the present invention, the assembling-related fractiondefectives in the assembling work of an article can be estimated withhigh accuracy for each of the part attaching works already at the stageof article design or a manufacturing process planning stage inprecedence to manufacture of the article, which in turn means that thosepart attaching works exhibiting high fraction defective coefficients canbe pinpointed without any appreciable difficulty. By improving the worksexhibiting high fraction defective coefficients, the assembling-relatedfraction defective can be reduced effectively. Thus, with the systemaccording to the present invention, design and manufacture of articlesor products can be realized with significantly enhanced reliability.

Many features and advantages of the present invention are apparent fromthe detailed description and thus it is intended by the appended claimsto cover all such features and advantages which fall within the truespirit and scope of the invention. Further, since numerous modificationsand combinations will readily occur to those skilled in the art, it isnot intended to limit the invention to the exact construction andoperation illustrated and described. By way of example, a storage mediumwhich stores data, information, program(s) and others for carrying outthe fraction defective estimation taught by the invention equally fallswithin the scope of the invention. Accordingly, all suitablemodifications and equivalents may be resorted to, falling within thespirit and scope of the invention.

1. A fraction defective estimating method for estimating an assemblingfailure potential (fraction defective) upon manufacturing of a partconstituting an article in precedence to manufacturing said part, saidfraction defective estimating method comprising the steps of: definingin advance a plurality of standard assembling operations by classifyingassembling operations involved in a manufacturing process asattachment-destined parts and attachment-subjected parts; setting foreach of said standard assembling operations a fraction defectivecoefficient represented by a numerical value indicative of a probabilityat which the assembling operation cannot be carried out without fail;representing apart under evaluation in terms of a combination of saidstandard assembling operations; and estimating the fraction defective ofsaid part under evaluation by adding together the fraction defectivecoefficients which said standard assembling operations have,respectively.
 2. A fraction defective estimating method according toclaim 1, further comprising the steps of: determining arithmetically asupplementary factor for correcting said fraction defective coefficientfor each of said standard assembling operations based on a combinationinformation of said standard assembling operations; and estimating thefraction defective by adding together the fraction defectivecoefficients acquired after having corrected said fraction detectivecoefficient for each of said standard assembling operations with saidsupplementary factor.
 3. A fraction defective estimating methodaccording to claim 1, further comprising the steps of: determiningarithmetically a supplementary factor for correcting said fractiondefective coefficient for each of said standard assembling operationsbased on the number of said standard assembling operations; andestimating the fraction defective by adding together the fractiondefective coefficients acquired after having corrected said fractiondefective coefficient for each of said standard assembling operationswith said supplementary factor.
 4. A fraction detective estimatingmethod according to claim 1, further comprising the steps of:determining arithmetically a supplementary factor for correcting saidfraction defective coefficient for each of said standard assemblingoperations based on property of an attachment-destined part and that ofan attachment-subjected part which are subjected to said assemblingoperations; and estimating the fraction defective by adding together thefraction defective coefficients acquired after having corrected saidfraction defective coefficient for each of said standard assemblingoperations with said supplementary factor.
 5. A fraction detectiveestimating method according to claim 1, further comprising the steps of:determining arithmetically a supplementary factor for correcting saidfraction defective coefficient for each of said standard assemblingoperations based on environmental conditions of a shop where assemblingwork is performed; and estimating the fraction defective by addingtogether the fraction defective coefficients acquired after havingcorrected said fraction defective coefficient for each of said standardassembling operations with said supplementary factor.
 6. A fractiondefective estimating method according to claim 1, further comprising thesteps of: determining arithmetically a supplementary factor forcorrecting said fraction defective coefficient for each of said standardassembling operations in dependence on presence or absence of a processfor confirming whether or not an assembling work has been carded outwithout fall after completion of said assembling work; and estimatingthe fraction defective by adding together the fraction defectivecoefficients acquired after having corrected said fraction defectivecoefficient for each of said standard assembling operations with saidsupplementary factor.
 7. A fraction defective estimating methodaccording to claim 1, further comprising the steps of: dividing saidstandard assembling operations into positioning operations andpost-positioning operations, operations succeeding to said positioningoperation; and determining arithmetically said fraction defectivecoefficient of said standard assembling operations based on combinationof fraction defective coefficients relative to said positioningoperations and fraction defective coefficients relative to saidpost-positionings.
 8. A fraction defective estimating method accordingto claim 1, further comprising the steps of: dividing said standardassembling operations into positioning operations and post-positioningoperations, operations succeeding to said positioning operation, whereinsaid fraction defective coefficients are set discretely in dependence onprecision degrees of said positioning operations even when saidpositioning operations are of a same type.
 9. A method of estimating anassembling failure potential (fraction defective) upon manufacturing anarticle which is constituted by a plurality of parts in precedence tomanufacturing said article, the method comprising the step of,estimating the fraction defective of said article based on results offraction defective estimations performed for a plurality of partsconstituting said article, wherein each fraction defective estimationperformed according to said fraction defective estimating method setforth in claim
 1. 10. A fraction defective estimating system forestimating an assembling failure potential (fraction defective) uponmanufacturing of parts constituting an article in precedence tomanufacturing said part, comprising: input means for receiving as inputsthereto information concerning assembling operations of said parts andinformation concerning properties of attachment-destined parts andattachment-subjected parts, respectively, which are to undergo saidassembling operations; fraction defective coefficient storing means forsetting and storing a fraction defective coefficient probability atwhich the assembling operation cannot be carried out without fail foreach of plural standard assembling operations defined by classifying inadvance the assembling operations involved in a manufacturing process;supplementarily factor storing means for storing supplementary factorsfor correcting the fraction defective coefficients of said standardassembling operations, respectively, on the basis of properties of saidattachment-destined parts undergoing said assembling operations andsupplementary factors for correcting the fraction defective coefficientsof said standard assembling operations, respectively, on the basis ofproperties of said attachment-subjected parts undergoing said assemblingoperations; program storing means for storing a computation program; andcomputing means for reading said computation program for executionthereof and reading out said fraction defective coefficients and saidsupplementary factors from said fraction defective coefficient storingmeans and said supplementary factor storing means, respectively, basedon information input through said input means for correcting saidfraction defective coefficients with said supplementary factors, tothereby compute the fraction defectives of said parts by adding togethersaid fraction defective coefficients after the correction thereof.
 11. Afraction defective estimating system according to claim 10, wherein saidcomputing means is so arranged as to estimate the fraction defective ofan article constituted by a plurality of parts based on a result of thefraction defective estimation performed for said plurality of partsconstituting said article.
 12. A computer program product for aninformation terminal having input means, output means and computingmeans, said information terminal including a device for a readablemedium, wherein a program code read out from said medium and executed bysaid computing means comprises the steps of: classifying in advanceassembling operations of parts in a manufacturing process to registersaid classified assembling operations as standard assembling operations;setting for each of said standard assembling operations a fractiondefective coefficient represented by a numerical value indicative of aprobability at which the assembling operation cannot be carried outwithout fail; representing a plurality of parts constituting an articleunder evaluation by in terms of combinations of said standard attachingoperations; and estimating assembling-related fraction defectives uponmanufacturing said plurality of parts constituting said article.
 13. Acomputer program product according to claim 12, further comprising thesteps of: estimating an assembling-related fraction defective uponmanufacturing said article based on the assembling-related fractiondefectives of said plurality of parts.